Precautions In Handling - Pontiac FIREBIRD 1972 Service Manual

1A-22 1972 PONTIAC SERVICE MANUAL
Since the compressor continues to operate, pressure is
reduced around the piston, at the equalizer line to the
expansion valve, and also beneath the spring-loaded valve
at the liquid bleed line. When the pressure differential
exceeds 5 to 12 psi, the liquid refrigerant and oil from the
evaporator bottom tank by-passes the evaporator core to
flow through the bleed valve (now open because of the 5
to 12 psi differential) and to the compressor. At the same
time warm air being forced by the blower through the
evaporator core provides more heat to the surface of the
core and thus causes the refrigerant inside the evaporator
tq boil. This increases the pressure within the evaporator
to such a point as to overcome atmospheric and spring
pressure above the diaphragm to move the piston to allow
refrigerant gas from the evaporator to pass through the
valve.
As the pressure differential at the liquid bleed valve falls
below 5 to 12 psi the valve closes, preventing refrigerant
and oil from by-passing the evaporator core. In this man-
ner, evaporator pressure is controlled and yet oil and re-
frigerant are always being returned to the compressor to
prevent the compressor from being damaged by sustained
operation at vacuum conditions where no oil would nor-
mally be returned to the compressor for lubrication. Re-
frigerant is then returned to the compressor where the
refrigeration cycle is repeated.
The pressure in the evaporator is so controlled at its lowest
pressure setting that any moisture condensing on the
evaporator surface will not freeze. If pressure drops below
the lowest controlled pressure setting, refrigerant and oil
by-pass the evaporator core, to flow directly through the
P.O.A. valve and then to the compressor.
Refrigerant is shipped and stored in metal drums. It is
serviced in drums and disposable cans.
It will be impossible to draw all the refrigerant out of the
drums. The use of warm water when charging the system
will assure the extraction of a maximum amount of refrig-
erant from the drum. Be sure to follow the instructions
under CHARGING THE SYSTEM.
PRECAUTIONS I N HANDLING REFRIGERANT
1. Do not leave drum of refrigerant uncapped.
2. Do not carry drum in passenger compartment of car.
3. Do not subject drum to high temperature.
4. Do not weld or steam clean on or near system.
5. Do not fill drum completely.
6. Do not discharge vapor into area where flame is ex-
posed.
7. Do not expose eyes to liquid.
All refrigerant drums are shipped with a heavy metal
screw cap. The purpose of the cap is to protect the valve
and safety plug from damage. It is good practice to replace
the cap after each use of the drum for the same reason.
If it is necessary to transmport or carry a drum of refriger-
ant in a car, keep it in the luggage compartment. If the
drum is exposed to the radiant heat of the sun, the result-
ant increase in pressure may cause the safety plug to re-
lease or the drum to burst.
For the same reason, the refrigerant drum should never be
subjected to excessive temperature when charging a sys-
tem. The refrigerant drum should be heated for charging
purposes by placing in 125°F. water. Never heat above
125°F. or use blowtorch, radiator or stove to heat the
drum.
Welding or steam cleaning near any of the refrigerant lines
or components of the air conditioning system could build
up dangerous and damaging pressures in the system.
If you ever have the occasion to fill a small drum from a
large one, never fill the drum completely. Space should
always be allowed above the liquid for expansion. If the
drum were completely full and the temperature was in-
creased, tremendous hydraulic force could be developed.
Discharging large quantities of refrigerant into a room can
usually be done safely as the vapor would produce no ill
effects. However, this should not be done if the area con-
tains a flame- producing device such as a gas heater or
running engines. While refrigerant normally is non-poiso-
nous, heavy concentrations of it in contact with a live
flame will produce a poisonous gas. The same gas will
attack all bright metal surfaces.
One of the most important cautions concerns the eyes.
Any liquid refrigerant which may accidentally escape is
approximately 2 1°F. below zero. If liquid refrigerant
should touch the eyes, serious damage could result. Al-
ways wear goggles to protect the eyes when opening refrig-
erant connections.
WARNING: If refrigerant liquid should strike the
eye, call a doctor immediately.
a. DO NOT RUB THE EYE. Splash the affected
area with quantities of cold water to gradually
get the temperature above the freezing point.
b. The use of an antiseptic oil is helpful in provid-
ing a protective film over the eyeball to reduce
the possibility of infection.
c. Obtain treatment as soon as possible, from a
doctor or eye specialist.
Should liquid refrigerant come in contact with
the skin, the injury should be treated the same as
skin which has been frostbitten or frozen.